JPH054328Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field This invention relates to a reference oscillation frequency adjustment device for a microcomputer used in electronic equipment with a built-in watch.

(B) Prior Art Conventionally, as a method for adjusting the reference oscillation frequency of a microcomputer used in an electronic device with a built-in clock, etc., for example, as shown in the block diagram of FIG. A method has been implemented in which the frequency counter 6 is directly connected and adjusted.

That is, when adjusting the oscillation frequency of the reference frequency oscillation circuit 11 formed inside the microcomputer 1, the frequency counter 6 is directly connected to the reference frequency oscillation circuit 11, and the trimmer capacitor 3 connected to the oscillation circuit 11 is connected. I made adjustments to match the crystal oscillation frequency.

However, as mentioned above, the reference frequency oscillation circuit 1
Connecting the frequency counter 6 etc. directly to 1 is as follows:
Even if a circuit (measuring instrument) with high input impedance was connected, the influence would not be zero and there would be a deviation from the actual oscillation frequency.

Therefore, the applicant of this invention previously proposed a reference oscillation frequency adjusting device as shown in the block diagram of FIG. 4 in order to eliminate the drawbacks of the conventional example.

The reference oscillation frequency adjustment device shown in FIG.
The microcomputer 1 includes a reference frequency oscillation circuit 11 formed inside the microcomputer 1, a crystal oscillator 2 externally connected to the reference frequency oscillation circuit 11, and a trimmer capacitor 3 (CV) for adjusting the crystal oscillation frequency. At the same time, the output of the reference frequency oscillation circuit 11 is passed through a frequency dividing circuit 12 (1/N) formed inside the microcomputer 1 to output the frequency-divided frequency signal to the output port 4 via the output buffer 13. It is configured as follows. Note that 5 is a test point connected to the output port 4.

By configuring as above, it is possible to connect the frequency counter 6 to the output port 4 (test point 5) and adjust the trimmer capacitor 3 connected to the reference frequency oscillation circuit 11 to match the crystal oscillation frequency. .

In this way, by configuring the output of the reference frequency oscillation circuit 11 to pass through the frequency dividing circuit 12 and dividing the frequency, and outputting the divided frequency signal to the output port 4, the oscillation frequency can be changed. During adjustment, the input impedance of the measuring device used, such as a frequency counter, can be ignored, allowing accurate adjustment.

(c) Problems to be solved by the invention However, the reference frequency oscillator shown in FIG. A new problem has arisen in that the noise mixes in as noise and affects peripheral circuits such as a broadcast receiving section or an audio signal amplification section.

This invention was made in view of the above points, and its purpose is to provide a system that can only be used when the main power supply of the device is off and the backup power supply of the microcomputer 1 is in backup operation.
An object of the present invention is to provide a reference oscillation frequency adjustment device capable of supplying to an output port 4 a frequency signal obtained by dividing the reference oscillation frequency by 1/N used for adjusting the reference frequency oscillation circuit of a microcomputer 1. .

(d) Means for solving the problem The reference oscillation frequency adjustment device according to this invention consists of a reference frequency oscillation circuit formed inside a microcomputer, a crystal oscillator externally connected to this reference frequency oscillation circuit, and a crystal oscillator. The device includes a trimmer capacitor for adjusting the frequency and a frequency dividing circuit for dividing the output of the reference frequency oscillation circuit, and is configured to output the oscillation frequency signal of the reference frequency oscillation circuit to an output port.

This invention provides, in the reference oscillation frequency adjustment device configured as described above, a determining means for determining whether the main power source is off and the backup power source of the microcomputer is in backup operation; supply prohibition means for prohibiting the supply of the oscillation frequency signal to the output port based on the output information of the microcomputer, and is configured to supply the oscillation frequency signal to the output port only during backup of the microcomputer, thereby solving the problem. We are trying to

(E) Effect Electronic equipment with a built-in microcomputer,
During actual operation, a frequency signal obtained by dividing the output of the reference frequency oscillation circuit by 1/N is not output to the output port. Therefore, side radiation does not interfere with peripheral circuits in actual operation.

In addition, when adjusting the reference frequency oscillation circuit of a microcomputer, it is necessary to determine that the main power supply of the electronic device is off and the backup power supply is in backup operation of the microcomputer, and then output the frequency divided by 1/N to the output port. A frequency signal can be provided and set to an adjustable state.

(F) Embodiment An embodiment of the reference oscillation frequency adjusting device according to the present invention will be described based on the block diagram schematically showing the configuration of FIG. 1.

In the figure, 1 is a microcomputer, which includes at least a reference frequency oscillation circuit 11.
A frequency dividing circuit 12 is formed. This reference frequency oscillation circuit 11 includes an externally connected crystal oscillator 2.
and a trimmer capacitor 3 for adjusting the crystal oscillation frequency. Further, the frequency dividing circuit 12 divides the reference oscillation frequency output from the reference frequency oscillation circuit 11 and supplies the divided frequency signal to the output port 4 via the output buffer 13. 5 is a test point connected to output port 4.

Reference numeral 14 denotes a determination circuit that determines whether the main power source of the electronic device incorporating the microcomputer 1 is off and the backup power source of the microcomputer 1 is in backup operation. Therefore, this discrimination circuit 14
When it is determined that the main power supply is off and the microcomputer is in backup mode,
The information signal is sent to the output buffer, and a 1/N frequency signal is supplied to the output port 4.
Further, when the discrimination circuit determines that a condition other than the above-mentioned conditions exists, an information signal to that effect is sent to the output buffer, and the supply of the frequency signal to the output port 4 is prohibited.

Next, the operation of the above embodiment will be explained based on the flowchart shown in FIG.

First, when adjusting the oscillation frequency of the reference frequency oscillation circuit 11 of the microcomputer 1, the main power of the electronic device is off and the microcomputer 1 is in backup operation using the backup power supply, so step S1 is set to ``YES''. , the process goes to step S2, the state in which the 1/N frequency signal is prohibited from being supplied to the output port 4 is canceled, and the 1/N frequency signal is no longer supplied to the output port 4.
The N-divided frequency signal is supplied to output port 4.

A frequency counter 6 is connected to this output port 4 (test point 5), and a reference frequency oscillation circuit 1 is connected to the output port 4 (test point 5).
By adjusting the trimmer capacitor 3 connected to 1, the crystal oscillation frequency can be matched.

At this time, the main power of the peripheral circuits such as the radio broadcast receiving section and the audio signal amplifying section placed in the same housing is off and not in actual operation, so the side radiation from output port 4 will have no effect. Not a problem.

On the other hand, when the peripheral circuit is in actual operation, the main power supply is off, so step S1 is "NO" and the process goes to step S3, where the 1/N frequency signal passes through the output buffer 13. frequency signals are prohibited from being supplied to output port 4.

As a result, when the peripheral circuit is in an actual operating state, side radiation due to the frequency signal does not occur from the output port 4, and noise generation due to side radiation can be prevented.

As is clear from the above embodiments, in the reference oscillation frequency adjustment device according to the present invention, when an electronic device with a built-in microcomputer is in actual operation, a frequency signal divided by 1/N is sent to the output port 4. It is no longer output.

(g) Effects of the invention According to the reference oscillation frequency adjustment device according to the invention, the output of the reference frequency oscillation circuit is passed through a frequency dividing circuit to be frequency-divided, and the frequency-divided frequency signal is
Since it is taken out to the output port only during backup operation of the microcomputer, it is possible to ignore the input impedance of measuring instruments such as frequency counters used when adjusting the oscillation frequency, and accurate adjustment can be made. I can do it, and also.
When the peripheral circuits such as the radio broadcast receiving section and the audio signal amplifying section are in actual operation, there is no side radiation from the output port, so it is possible to improve the S/N ratio and prevent the occurrence of beats.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the reference oscillation frequency adjusting device according to the invention,
FIG. 1 is a block diagram, and FIG. 2 is a flowchart. FIG. 3 is a block diagram showing a conventional example. FIG. 4 is a block diagram of a reference oscillation frequency adjusting device previously proposed by the applicant of this invention. 1... Microcomputer, 2... Crystal oscillator, 3... Trimmer capacitor, 4... Output port, 5... Test point, 6... Frequency counter, 11... Reference frequency oscillation circuit, 12... Frequency division Circuit, 13... Output buffer, 14... Discrimination circuit.

Claims (1)

[Claims for Utility Model Registration] A reference frequency oscillation circuit formed inside a microcomputer, a crystal oscillator externally connected to this reference frequency oscillation circuit, a trimmer capacitor for adjusting the crystal oscillation frequency, and a reference frequency oscillation circuit. A reference oscillation frequency adjusting device comprising a frequency dividing circuit that divides the output of the circuit, and configured to output an oscillation frequency signal of the reference frequency oscillation circuit to an output port, the device being configured to output an oscillation frequency signal of the reference frequency oscillation circuit to an output port, the device being configured to and a determining means for determining whether or not a backup power supply of the microcomputer is in backup operation, and a supply prohibiting means for prohibiting the supply of an oscillation frequency signal to the output port based on output information of the determining means, A reference oscillation frequency adjustment device characterized in that it is configured to supply an oscillation frequency signal to an output port only during backup of a microcomputer.